Alexander Kluge

Acute Pulmonary Embolism to the Subsegmental Level: Diagnostic Accuracy of Three MRI Techniques Compared with 16-MDCT

OBJECTIVE The purpose of this study was to assess the individual and combined usefulness of MRI techniques in cases of acute pulmonary embolism and to compare the usefulness of these techniques with that of 16-MDCT. SUBJECTS AND METHODS Sixty-two patients with symptoms indicating acute pulmonary embolism underwent an MRI protocol that progressed from real-time MRI through MR perfusion imaging to MR angiography. The results were compared with those of 16-MDCT, which was the reference standard. Thoracic incidental diagnoses other than pulmonary embolism also were sought with CT and MRI. RESULTS Pulmonary embolism was diagnosed with CT in 19 patients for totals of 90 lobar, 245 segmental, and 434 subsegmental arteries. On a per-patient basis, the sensitivities of real-time MRI, MR angiography, MR perfusion imaging, and the combined protocol were 85%, 77%, 100%, and 100%, respectively. The specificities were 98%, 100%, 91%, and 93%. The kappa values in a comparison of the MR techniques with CT were 0.89, 0.87, 0.86, and 0.9. On a per-embolus basis, the sensitivities of real-time MRI, MR angiography, and MR perfusion imaging for lobar pulmonary embolism were 79%, 62%, and 100%. The sensitivities for segmental pulmonary embolism were 86%, 83%, and 97%, respectively. MR perfusion imaging had a sensitivity of 93% for subsegmental pulmonary embolism. Eight of nine incidental findings revealed on CT were also subsequently diagnosed with real-time MRI. MRI failed to reveal a case of emphysema. Mean MRI examination time was 9 minutes 56 seconds. CONCLUSION The combined MR protocol is both reliable and sensitive in comparison with 16-MDCT in the diagnosis of pulmonary embolism. MR perfusion imaging is sensitive for the detection of pulmonary embolism, whereas real-time MR and MR angiography are specific.

Noninvasive Quantification of Brain Edema and the Space-Occupying Effect in Rat Stroke Models Using Magnetic Resonance Imaging

Background and Purpose— Brain edema is a life-threatening consequence of stroke and leads to an extension of the affected tissue. The space-occupying effect due to brain edema can be quantified in rat stroke models with the use of MRI. The present study was performed to test 2 hypotheses: (1) Can quantification of the space-occupying effect due to brain edema serve as a noninvasive measure for brain water content? (2) Does morphometric assessment of brain swelling allow determination of true infarct size on MRI after correction for the space-occupying effect of edema? Methods— Thirty rats were subjected to permanent suture middle cerebral artery occlusion. MRI was performed after 6 or 24 hours, and hemispheric swelling was assessed morphometrically. Interobserver and intraobserver agreements were determined for MRI measurements. In study I, the space-occupying effect due to brain edema was correlated with the absolute brain water content by the wet/dry method. In study II, lesion volumes corrected and uncorrected for edema were calculated on MRI and on TTC staining and compared. Results— Interobserver and intraobserver agreements for MRI measurements were excellent (r ≥0.97). Brain water content and hemispheric swelling correlated well after 6 and 24 hours (r ≥0.95). Corrected lesion volumes correlated with r =0.78 between TTC staining and MRI. Without edema correction, lesion volumes were overestimated by 20.3% after 6 hours and by 29.6% after 24 hours of ischemia. Conclusions— Morphometric assessment of hemispheric swelling on MRI can determine the increase in absolute brain water content noninvasively and can also provide ischemic lesion volumes corrected for brain edema.

Prostate carcinoma: diffusion-weighted imaging as potential alternative to conventional MR and 11C-choline PET/CT for detection of bone metastases.

In a technical development study approved by the institutional ethics committee, the feasibility of fast diffusion-weighted imaging as a replacement for conventional magnetic resonance (MR) imaging sequences (short inversion time inversion recovery [STIR] and T1-weighted spin echo [SE]) and positron emission tomography (PET)/computed tomography (CT) in the detection of skeletal metastases from prostate cancer was evaluated. MR imaging and carbon 11 ((11)C) choline PET/CT data from 11 consecutive prostate cancer patients with bone metastases were analyzed. Diffusion-weighted imaging appears to be equal, if not superior, to STIR and T1-weighted SE sequences and equally as effective as (11)C-choline PET/CT in detection of bone metastases in these patients. Diffusion-weighted imaging should be considered for further evaluation and comparisons with PET/CT for comprehensive whole-body staging and restaging in prostate and other cancers.

Diffusion-Weighted Magnetic Resonance Imaging and Neurobiochemical Markers After Aortic Valve Replacement Implications for Future Neuroprotective Trials?

Background and Purpose— Cardiac surgery carries a high risk of neurological complications; therefore, these patients would be an appropriate target population for neuroprotective strategies. In this study, we evaluated postoperative diffusion-weighted imaging (DWI) as a potential surrogate marker for brain embolism and its relationship to neurobiochemical markers of brain injury. Methods— Of a total of 45 consecutive patients undergoing aortic valve replacement, 37 completed preoperative and postoperative MRI. At the time of the MRI studies, serum S100&bgr; and neuron-specific enolase concentrations were determined. Preexisting T2 and postoperative DWI lesion volumes were quantified. All patients had a blinded neurological examination before and after operation. Results— New perioperative DWI lesions were present in 14 patients (38%), of whom only 3 developed focal neurological deficits. Eighteen small lesions were found in the white matter or vascular border zones in all but 2 patients with territorial stroke. The appearance of new DWI lesions correlated with age, pre-existing T2 lesion volume, and postoperative S100&bgr; concentrations on days 2 to 4 after surgery. In a forward stepwise canonical discrimination model, only T2 lesion volume was selected as a relevant variable. Conclusions— The incidence of postoperative DWI lesions in aortic valve replacement is high, and a suitable marker for neuroprotective trials would be a reduction in the number of such lesions. The volume of preexisting T2 lesions is related to the development of perioperative DWI lesions.

Complications and Pitfalls in Rat Stroke Models for Middle Cerebral Artery Occlusion A Comparison Between the Suture and the Macrosphere Model Using Magnetic Resonance Angiography

Background and Purpose— Investigating focal cerebral ischemia requires animal models that are relevant to human stroke. Complications and side effects are common among these models. The present study describes potential pitfalls in 3 techniques for middle cerebral artery occlusion (MCAO) in rats using magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA). Methods— Rats were subjected to temporary MCAO for 90 minutes using the suture technique (group I; n=10) or to permanent MCAO using the suture technique (group II; n=10) or the macrosphere technique (group III; n=10). Clinical evaluation was performed after 3 hours and 24 hours. After 24 hours, animals underwent MRI and MRA to determine lesion size and the intracranial vascular status. Results— Hemispheric lesion volume was significantly smaller in group I (14.6%) compared with groups II (35.2%; P<0.01) and III (21.3%; P<0.05). Two animals (1 each in group II and III) did not demonstrate neurological deficits and had no lesion on MRI and a patent MCA main stem on MRA. Subarachnoid hemorrhage was detected in 2 animals (1 each in group I and II). MRA indicated a patent MCA main stem in 2 animals (group II), although both rats displayed neurological deficits. Hypothalamic infarction with subsequent pathological hyperthermia was detected in all animals in group II and in 1 rat in group III. Conclusions— Model failures occurred frequently in all groups. MRI and MRA helps to identify animals that need to be excluded from experimental stroke studies.

Ankylosing spondylitis and bone mineral density—what is the ideal tool for measurement?

Ankylosing spondylitis (AS) is characterised by chronic inflammation and partial ossification, yet vertebral fractures due to osteoporosis, although common, are frequently unrecognised. The aim of this study was to (1) show the frequency of changes in the progress of osteopenia/osteoporosis in AS depending on duration and stage of the disease and (2) assess the ranking of two different methods of bone density measurement in this clinical pattern. We measured bone density in 84 male and female patients with both dual X-ray absorptiometry (DXA) and single energy quantitative computed tomography (SE-QCT). In the initial and advanced stages of the disease, a high decrease in axial bone density could be verified (DXA: osteopenia in 5% and osteoporosis in 9.2%; SE-QCT: osteopenia in 11.8% and osteoporosis in 30.3%). Peripheral bone density decrease as in osteopenia could be proven in 17.6% by DXA measurement. With SE-QCT, a decrease in vertebral trabecular bone density could already be observed in the initial stage and continued steadily during the course of the disease; cortical bone displayed the same trend up to stages of ankylosis. With DXA, valid conclusions are more likely to be expected in less marked ankylosing stages of AS. In stages of advanced ankyloses in the vertebral region (substantial syndesmophytes), priority should be given to SE-QCT, due to the selective measurement of trabecular and cortical bone. The DXA method often yields values that are too high, and the replacement of vertebral trabecular bone by fatty bone marrow is not usually recorded as standard. There may already be an increased risk of bone fracture in AS in osteopenia on DXA along with an osteoporosis already established on SE-QCT.

Percutaneous Pulmonary Vein Stenting for the Treatment of Severe Stenosis After Pulmonary Vein Isolation

Introduction: Pulmonary vein stenosis (PVS) is a potential complication of pulmonary vein isolation (PVI) using radiofrequency energy. The aim of our study was the evaluation of the severity and long‐term outcome of primary angioplasty and angioplasty with pulmonary vein stenting for PVS.

Puncture of the popliteal artery using a Doppler-equipped (SMART) needle in transpopliteal interventions

Abstract. The puncture of the popliteal artery for percutaneous intervention is usually performed under fluoroscopic guidance or with the assistance of percutaneous ultrasound to avoid accidental arteriovenous fistulas. We present our experience in 119 cases with the use of a Doppler ultrasound equipped Seldinger needle (SMART needle) for the detection and puncture of the popliteal artery. In 119 interventions in 103 patients, the puncture of the popliteal artery was performed with the SMART needle. The puncture was successful in 94.1% (112 of 119) of cases. Six (5.2%) complications occurred during puncture: four hematomas (no therapy required) and two arteriovenous fistulas (treated by manual compression solely). The subsequent 112 interventions in 103 patients [98 percutaneous transluminal angioplasty (PTA), 8 PTA with stent implantations, 4 PTA with thrombolysis, 2 thrombolyses] were technically successful in 79.5% (89 of 112). The SMART-needle-guided popliteal puncture showed to be safe, fast, and easy to perform, which allowed the use of this technique by radiologists in training. The rates of success and complications are comparable to reported results for other visualization techniques, whereas time, effort, and training required are lower. This may contribute to a more widespread use of the transpopliteal access for interventions and therefore offers a therapeutic option in addition to vascular surgery.

Cardiac metastasis of a renal cell adenocarcinoma investigated by cardiac magnetic resonance imaging

Alexander Kluge, MD Department of Cardiology Kerckhoff Heart Center Bad Nauheim, Germany Sirs: Primary and secondary cardiac malignancies are rare. New imaging methods like cardiac magnetic resonance imaging (MRI) play an important role in early diagnosis and differentiation of cardiac masses. A case of 68-year-old woman with a cardiac metastasis of renal cell adenocarcinoma is presented. The unusual findings on cardiac MRI which nevertheless allowed the identification and characterization of this cardiac malignancy together with the clinical history are reported in detail. Case report